Late-onset Alzheimer's disease: The most common form of Alzheimer's disease, usually occurring after age 65. Late-onset Alzheimer's disease affects almost half of all people over the age of 85.

Late stage: Designation given when dementia symptoms have progressed to the extent that a person has little capacity for self-care.

Lewy body dementia: A dementing illness associated with protein deposits called Lewy bodies, found in the cortex of the brain.

Living trust: A legal document that allows an individual (the grantor or trustor) to create a trust and appoint someone else as trustee (usually a trusted individual or financial institution) to carefully invest and manage his or her assets.

Living will: A legal document that expresses an individual's decision on the use of artificial life support systems.

Long-term care: A comprehensive range of medical, personal, and social services coordinated to meet the physical, social, and emotional needs of people who are disabled or ill for extended periods of time.

Magnetic resonance imaging (MRI): A test that produces high-quality images of the body's internal structures without the use of X-rays. MRI uses a large magnet, radio waves, and a computer to produce these images.

Medicaid: A program sponsored by the federal government and administered by states that is intended to provide health care and health-related services to low-income individuals.

Medicare: A federal health insurance program for people age 65 and older and for individuals with disabilities.

Metabolism: The complex chemical and physical processes of living organisms that promote growth, sustain life, and enable other bodily functions to take place.

Multi-infarct dementia (MID): A form of dementia, also known as vascular dementia, caused by a number of strokes in the brain. These strokes can affect some intellectual abilities, impair movement and walking skills, and cause an individual to experience hallucinations, delusions, or depression. The onset of MID is usually abrupt and often progresses in a stepwise fashion. Individuals with MID are likely to have risk factors for strokes, such as high blood pressure, heart disease, or diabetes. MID cannot be treated; once nerve cells die, they cannot be replaced. However, risk factors can be treated, which may help prevent further damage.